As an alternative to burial, cremation is no longer green enough, say environmentalists, because it releases smoke and mercury, and thus the industry is considering "promession," in which the body is frozen in liquid nitrogen to minus-320 degrees and then shaken until it disintegrates into powder. For green burials, the United States has at least six cemeteries that require biodegradable casings and for bodies to be free of embalming chemicals. The Forever Fernwood cemetery in Mill Valley, Calif., goes even further, according to an October Los Angeles Times story, banning grave markers, but, said the owner, "We issue the family a Google map with the GPS coordinates" so they can find their loved one.